PIC LC meter improvements add Li-Ion battery and charging circuitry

[Trax] needed an LC meter and decided to use a tried-and-true design to build his own. The only problem was that he didn’t want to be tied to a bench supply or power outlet, which meant a bit of auxiliary design was in order. What he came up with is the battery-powered LC meter you see above.

The core of the original [Phil Rice] design remains the same, with slight modifications to drive a different model of character LCD. The code is mostly unchanged, but some calibration routines became necessary after [Marko] noticed bugs in the behavior after power cycling. Now the device will perform what amounts to a hardware reset about 700ms after powering on or changing between inductance and capacitance measuring functions. The project box is quite small, and to get everything to fit [Marko] sourced the Lithium Ion battery from a Bluetooth headset. He needs 5V for the LCD screen so he used a TPS61222 boost converter. To top off the battery he’s included a MAX1811 single-cell Li-ion charger, which has a couple of status LEDs visible through the case as seen above.

An LC meter measures inductance (L) and capacitance (C). Most multimeters will only measure resistors and large valued capacitors, which makes this a neat project for figuring out component values for analog design projects.

Very neat project both in usefulness and build, it’s always nice to see an end product from a DIY build that looks like it could’ve just been bought from a shop.

One thing that always strikes me about the alphanumeric displays on the market is the sheer size of the accompanying circuitboard(s) needed to drive them, it makes you wonder how small you could make an LCD meter using the miniature 16×2 screen used on the neat DIY scientific wristwatch

It also solves the problem of running a 5v LCD from a 3v coin cell, using a very simple boost circuit consisiting of a capacitor, two diodes and a PWM signal, as shown on the uWatch schematic and noted in tip 10 of a rather useful set of tips & tricks from Microchip: http://ww1.microchip.com/downloads/en/devicedoc/40040b.pdf